1. Field of the Invention
The present invention relates generally to electrical wiring devices, and particularly to devices that include relatively high current USB charging receptacles.
2. Technical Background
Electrical distribution systems deliver power throughout a building from the power source to electrical wiring devices. Electrical wiring devices are connected to the electrical distribution system by way of a plurality of terminals and deliver power from the power source to a load. One or more electrical wiring devices can be mounted to a device box depending on the size of the device box. Once the electrical wiring device is installed inside the device box, a cover plate is disposed over the electrical wiring device to complete the installation. Electrical wiring devices typically include receptacles, switches, ground fault circuit interrupters, GFCIs, arc fault circuit interrupters, AFCIs, transient surge suppressors, TVSSs, occupancy sensors, dimmers, timers, and low voltage devices. These devices were introduced to the market place as the state of the art developed over time. Of course, the state of the art continues to develop.
Indeed, the public has witnessed a technological revolution during the past twenty years or so. During this time, personal computers were introduced to the public and the Internet evolved from an obscure military/research network into the global phenomenon it is today. Computer networks, public switched telephone networks (PSTN), wireless networks as well as individual users send and receive all types of data via the Internet—planet earth is wired—nowadays, almost everyone has at least one processor based device that they use to “get on line.” One should keep in mind, however, that the interconnectivity that we all enjoy was not always this easy.
In the past, interconnecting computers and the various peripheral devices (such as printers, mice, keyboards, and modems) was quite challenging. In early computers, printers were designed to be connected via a parallel printer port, and usually, the computer only supported one printer device. Modems on the other hand, typically used a slow serial port (e.g., 56 kbps) that might have to be shared with discrete devices such as cameras, etc. The universal serial bus (“USB”) emerged as a solution to the problem of connecting various peripheral devices to computers. The USB was designed as a standardized easy-to-use, plug and play connector that can be used to connect up to 127 devices to a computer.
And now there is yet another revolution hard on the heels of the first one. The second revolution, of course, is the wireless revolution and it presents its own set of problems. In the recent past, e.g., people would do their computing from a desk top computer that was hard wired into a wireline network (e.g., CATV, PSTN) and obtained electrical power from a nearby receptacle. Now, people are accessing the Internet wirelessly by way of a variety of wireless devices that includes cell phones, Internet phones, portable lap top or netbook type computers, personal digital assistants, MP3 players, gaming devices and the like. Moreover, cloud computing is now being introduced such that users can access their personal data from “the cloud.” While wireless users can access telecommunication and data services wirelessly, Tesla's dream of providing electrical power in this manner has not been realized. Stated differently, all of these portable devices must obtain power from batteries that, in turn, must be recharged periodically.
In one approach that has been considered, the portable electronic devices referred to above would come with their own power charging devices. Battery chargers are typically heavy and bulky because they need to convert high voltage AC power into the low voltage DC employed by the portable device. The AC/DC conversion thus requires a step down transformer. One of the drawbacks associated with this approach is that it requires the users to lug the separate battery charger along with them everywhere they go or risk battery depletion.
In another approach, a wall mounted electrical receptacle configured to provide both AC power service and low voltage DC power has been considered in light of the drawbacks associated with portable battery chargers. This approach conveniently provided a step down transformer in combination with an AC/DC conversion circuit in an electrical wiring device form factor. One of the drawbacks of this approach relates to the wiring device size and charging current tradeoff. Stated differently, the amount of charging current drawn by the portable device-under-charge is limited by the size of the transformer in the electrical wiring device. The size of the transformer in the electrical wiring device is limited in turn by the size of the electrical wiring device itself. The form factor of an electrical wiring device is constrained by the size of a single gang device box. Heretofore, these size limitations have precluded wall mounted charging devices from providing a charging current of more than 750 mA. While 750 mA may be an appropriate charging current for some of the older portable devices, it is not appropriate for some of the newer devices that draw a larger charging current. Stated differently, the instant inventors have found that some of the newer devices require a much greater charging current and will not, in fact, charge in response to, e.g., a 750 mA current. Other devices will take an inordinate amount of time before they are completely charged.
In yet another approach, a metal raceway system configured to provide both AC power service and higher charging current DC power has been considered in light of the drawbacks associated with relatively low current electrical wiring devices described above. The metal raceway embodiment is also applicable to power strip or power cord applications. Both of these form factors are not limited by the aforementioned size constraints. However, both of these approaches have their own drawbacks. While metal raceways may be appropriate for commercial and industrial applications, they are not aesthetically pleasing in the home environment. And the use of a power strip device takes the problem full circle back to the portable battery charger. No one wants to lug around a separate battery charger or a power strip device with them when they are traveling.
What is needed, therefore, is a wall mountable electrical wiring device that can provide multiple USB receptacles that provide a relatively high charging current for the newer portable devices being introduced to the market. Alternatively, what is needed is a wall mountable electrical wiring device that can provide at least one USB receptacle in combination with a power control device such as an AC outlet receptacle or a switching device.